High temperature lubricating greases



2,898,300 Patented Aug. 4, 1959 HIGH TEIVIPERATURE LUBRICATING GREASES James H. Norton, Corunna, Ontario, and Samuel B. Baker, Sarnia, Untario, Canada, assignors to Esso Research and Engineering Company, a corporation of Delaware N Drawing. Application April 25, 1957 Serial No. 655,022

6 Claims. (Cl. 252-499) This invention relates to lubricating compositions. Particularly, it relates to greases which. are thickened with the reaction product of arylene isocyanates with organic-substituted acids of phosphorus having at least one free hydroxy group.

It has been found that lubricating oils thickened with the reaction product of arylene isocyanates and organicsubstituted oxygen-containing acids of phosphorus having free hydroxy groups, will form excellent high dropping point greases having good water resistance. Furthermore, upon charring, these greases do not form a metallic ash, such as is formed by conventional metal soap greases, and are therefore particularly useful in high temperature applications where a metallic ash or residue would be undesirable.

The arylene isocyanates which, may be used in the invention are preferably arylene diisocyanates having the general formula:

wherein R represents unsubstituted arylene radicals such as phenylene, biphenylene, naphthylene and diphenylmethane radicals, and substituted arylene radicals such as those substituted with one or more alkyl or alkoxy radicals containing 1 to 4, e.g. 1 to 2, carbon atoms per substituent group. Examples of these compounds include 1,4-phenylene diisocyanate; 1,3-pheny1ene diisocyanate; 3,3'-dirnethyl-4,4'-biphenyler1e diisocyanate; 2 'butyl, 3- methyl-S,4'-biphenylene diisocyanate; 2decyl-1,4-phenylene diisocyanate; 4-methyll,3-phenyl diisocyanate; 4- methyl-2,6-phenyl diisocyanate; diphenylmethane-4,4-diisocyanate; 3,3'-dimethyldiphenylmethane-4,4' diisocyanate; 3,3'-dimethoxy-4,4'-biphenylene diisocyanate; etc, Various polymers of the above type of materials may also be used such as a polyaryl polyisocyanate of the formula:

LE1 OCNO-CHT Iowa The phosphorus-containing compounds which may be reacted with the diisocyanates include those oxygen-containing acids of phosphorus which have been substituted with alkyl radicals. These materials have the following general formula:

wherein n is 0 or 1; X is R, OR or OH; Y is either R or OR; said R representing the same or different, straight or branched-chain alkyl radicals containing 1 to 18, (2g. 4 to 8 carbon atoms. The total number of carbon atoms in the compound will be about 1 to 54, a g. 4 to 24. R may 2 be methyl, ethyl, isopropyl, n-pentyl, n-octyl, n-dodecyl, octadecyl, etc. Specific compounds of the above formula will include alkyl-substituted phosphonous acids, i.e. RP(OH) such as methyl phosphonous acid or n-pentyl phosphonous acid; alkyl-substituted phosphinous acid, i.e. R P(OH), such as methyl, ethyl phosphinous acid, di-n-octyl phosphinous acid; alkyl-substituted phosphonic acids, i.e. RPO(OH) for example, ethane phosphonic acid; alkyl-substituted phosphinic acid, i.e. R POLOH), such as methyl, ethyl phosphinic acid; monoesters of phosphinous acids, i.e. RP(OR)OH, such as the monoethyl ester of methyl phosphinous acid; diesters of phosphorous acid, i.e. (RO) POH, such as the dimethyl ester of phosphorous acid, the methyl ethyl diester of phosphorus acid; monoesters of phosphoric acid, i.e. ROPO(OH) such as monoethyl di-acid phosphate; diesters of phosphoric acid, i.e. (RO) PO(OH), such as dirnethyl mono-acid phosphate; etc.

The compositions of the present invention therefor will consist of a lubricating oil containing a grease-thick ening proportion, such as about 5 to 70, e.g. 20 to 60 weight percent, based on the total weight of the lubricating composition, of the reaction product of an arylene diisocyanate and an alkyl-substituted phosphorus compound. While not essential, it is preferred to react these materials in a molar ratio such that there is about one isocyanate group available per reactive hydrogen in the phosphorus compound (i.e. per hydroxy group).

The lubricating oil used in the lubricants of the invention may be either a mineral lubricating oil or a synthetic lubricating oil. Operable synthetic lubricating oils include esters of monobasic acids (e.g. ester of C Oxo acid), esters of dibasic acids (e.g. bis-(Z-ethylhexyl) sebacate); esters of glycols (e.g. C Oxo acid diester of tetraethylene glycol); complex esters (e.g. the complex ester formed by reacting one mole of sebacic acid with wherein R represents substituted or unsubstituted alkyl, aryl, haloaryl, alkylaryl, arylalkyl, cycloal-kyl radicals containing between about 1 to 8 carbon atoms per radical. Specific examples of such oils include the phenylmethylsilicone polymer, dimethylsilicone polymer, chlorophenylmethylsilicone polymer, etc. These materials are known in the art and are available under trade names such as DC (Dow Corning) F-ZSS Silicone Fluid, DC F-60 Silicone Fluid, DC 550 Silicone Fluid, etc. A preferred silicone oilis Dow'Corning 550 Silicone Fluid, which'has 1 a viscosity at F. of about 350 SSU and is a phenylmethyl silicone polymer oil having a methyl to phenyl,

ratio of about 0.6 to 1.0. v

Conventional additives may also be added to the grease composition such as oxidation inhibitors, forexample, phenyl alpha naphthylamine, phenothiazine; metal deactivators such as disalicylal' propylenediamine, zinc dibutyl dithiocarbamate;corro sion preventives such as sodium sulfonate, manganese naphthenate, sorbitan monoleate, sorbitan monostearate, and other additives.

In general, the lubricating compositions of the invention are readily prepared in situ by dispersing the arylene diisocyanate and the alkyd-substituted phosphorus-containing acid in a portion or all of the lubricating oil, then heating the dispersion until the reaction is substantially complete, e.g. about 150 to 400 F., for about A to 24hours. The time of heating is, of course, dependent upon the temperature employed. However, the completion of the reaction is indicated when there is no further increase in the consistency of the reaction mixture upon heating. Generally, after the reaction is believed to be completed, it is desirable to maintain the reaction mixture at high temperatures, say about 300 to 400 F. for about to 30 minutes, in order to completely dehydrate the product and to ensure the completion of the reaction. The resulting product may then be cooled to a temperature of about 100 to 200 F. and conventional lubricating additives maybe added if desired. The product may then be homogenized at a high rate of shear before cooling .to room temperature. The homogenization can be carried out, for example, by using a Gaulin homogenizer operating at about 3000 to 6000 p.s.i.g., a Morehouse mill, a Charlotte mill, etc.

The grease can also be prepared by preforming the thickener by reacting the aryl diisocyanate with the alkylsubstituted phosphorus-containing acid in the presence of an inert solvent, such as heptane, etc., at elevated temperatures, e.g. about 100 .to 300 -F. for about 1 to 4 hours or until the reaction is completed as evidenced by no further change in consistency of reaction product upon continued heating. The solvent may then be evaporated in order to recover the reaction product. A grease may then be prepared by dispersing the above reaction product by milling the solid reaction product and the oil two or three times through a Travis disperser, a Morehouse mill, or other mills.

The invention will be further understood by the following eXamples which include preferred embodiments of the invention.

Example I A grease was prepared by dispersing gm. of 'bitolylene diisocyanate and gm. of dibutyl hydrogen phosphrte in 50 gm. of a silicone oil (Dow Corning 550 Silicone Fluid), followed by heating on a steam bath so as to maintain a temperature between about 150 to 200 F. for about 24 hours. The grease was then allowed to cool, while stirring, to room temperature and was then inspected.

Example II A grease was prepared'by dispersing 20 gm. of bitolylene diisocyanate and 30'gm. of di(2-ethylhexyl) hydrogen phosphite in 50 gm. of Dow Corning 550 Silicone Fluid, followed by heating to 300 F. for about 1 hour. The grease was then allowed to cool to room temperature.

Example III A grease was prepared in a manner similar to that of Example II, except that the dispersion was heated to 400 F. for about /2 hour.

Example IV 1 3,3-dimethyl-4,4-biphenylene diisocyanate. 2 Phenylmethyl silicone polymer oil having a viscosity at 100 F. of 350 SUS and a methyl to phenyl ratio of about 0.0 to 1.0.

As seen from the above table, non-metallic, high dropping point greases were formed using either a synthetic oil or a mineral oil.

To further illustrate the invention, other greases may be prepared as follows: For example, a mineral oil (300 SUS at 100 F.) may be thickened to a grease with 40 Weight percent, based on the total composition, of thickener which may be prepared by reacting 1,3-phenylene diisocyanate with monoethylene di-acid phosphate in equimolar proporations, in situ in the lubricating oil, at a temperature of about 300 F. for about 1 hour. Similarly a grease may be prepared in the same manner as just described, except that one molar proportion of 3,3 dimethoxy 4,4'-diphenylenemethane diisocyanate may be used in place of the 1,3-phenylene diisocyanate, while two molar proportions of the di-n-octyl phosphinous acid may be used in place of the monoethyl di-acid phosphate.

What is claimed is:

1. A lubricant comprisingalubricating oil and a greasethickening amount of the reaction product of a diisocyanate having the general formula:

wherein R is an arylene radical and an alkyl substituted oxygen-containing acid of phosphorus having at least one hydroxy group attached to the phosphorus atom, and wherein said reaction product is prepared by reacting said diisocyanate and said acid of'phosphorus in a molar ratio such that there is about one isocyanate group available per hydroxy group, .at a temperature of about 150 to 400 F. for about A to 24 hours in situ in said lubricating :oil.

2. A lubricating grease comprising a lubricating oil and about 5 :to'70' weight percent, based on the total composition, ofthe reaction product of a diisocyanate having the general formula:

wherein R is selected from the group consisting of unsubstituted aryl radicals, alkyl substituted arylene radicals and alkoxy substituted arylene radicals, said substituent groups each containing 1 to 4 carbon atoms, and an alkyl substituted oxygen-containing acid of phosphorus having at least one hydroxy group attached to the phosphorus atom, wherein said reaction product is prepared by reacting said diisocyanate and said acid of phosphorus in a molar ratio such that there is about one isocyauatc group available per hydroxy group, at a temperature of about 150 to 400 F., in situ in said lubricating oil for about /4 to 24 hours and cooling to form said grease composition.

3. A grease according to claim 2, wherein said lubrieating oil is selected from the group consisting of mineral lubricating oil and silicone polymer oil having lubricating oil viscosity.

gen phosphite, said alkyl groups containing 1 to 18 carbon atoms.

5. A lubricating grease comprising a lubricating oil and about 20 to 60 Weight percent, based on the total composition of the reaction product of a methyl substituted biphenylene diisocyanate and a dialkyl hydrogen phosphite, said alkyl groups each containing 4 to 8 carbon atoms.

6. A process for preparing a grease composition which comprises dispersing an aryl diisocyanate having the general formula:

wherein R is an arylene radical and an alkyl substituted oxygen-containing acid of phosphorus having at least 1 hydroxy group attached to the phosphorus atom, in a References Cited in the file of this patent UNITED STATES PATENTS Swakon et a1. June 14, 1955 OTHER REFERENCES I. Am. Chem. Soc., vol. 77 (1955), p. 3813. I Am. Chem. Soc., vol. 78, No. 4 (1956), pp. 842 and 843. 

1. A LUBRICANT COMPRISING A LUBRICATING OIL AND A GREASETHICKENING AMOUNT OF THE REACTION PRODUCT OF A DIISOCYANATE HAVING THE GENERAL FORMULA: 